Pipe-threading die.



PATENTED APR. 21, 1908.

J. P. GRUDGINTON.

PIPE THRBADING DIE.

APPLICATION FILED 1mm, 1901.

THE nunms PETERS cm. WASH! NGION, n. c.

UNITED s T s PATENT OFFICE.

JAMES F. ORUDGINTON, OF BRIDGEPOBT, CONNECTICUT.

PIPE-THREADING DIE.

Specification of Letters Patent.

Application filed November 4, 1907.

Patented April 21, 1908.

Serial No. 400,490.

following is a specification.

Myinvention relates to pipe threading dies, and its object is so toconstruct the dies that they will not only cut and back off freely, butcannot gouge or dig in. To this end, the threaded bits, when the diesare in operative position, are located an equal distance from the centerof the pi e with two opposite bits cutting the threa while the other twobits act as trailers-to steady the cutting bits and prevent theirgouging. Each section of the die carries a cutting bit and a trailingbit relieved in opposite directions.

To enable others to understand my invention, reference is had to theaccompanying drawings, in which:

Figure 1 represents a broken rear view of .'a pair of dies and the endof a pipe with the dies in cutting position; Fig. 2 is a detail view ofone of thedies looking in the direction of the arrow shown at Fig. 1;Fig. 3 is a front elevation of the dies, one of which is shown asbroken.

1 and 2 are sections of dies of the common form adapted to be insertedin a die stock to be operated either by hand or power. Integral with thedies are the threaded bits 1 1 2 and 2 1 and 2 represent the cuttingbits, while 1 and 2 are the trailing bits. The clearance curves (1 and bof the bits of the die section 1 are projected in opposite directionswith respect to each other,

and this is true with respect to the curves 0 and d of the die section2.

The cutting edges e f of the cutting bits 1 and 2 andthe trailing edgesg h of the bits 1 and 2 are all an equal distance from the center of thepipe 3 when the dies are in cutting position with respect to the pipe.

As each bit is provided with a full thread back of its mouth with thetrailing edges 9 h andthe cutting edges e f an equal distance from thecenter of the ipe,-it is uite evident that the trailing eilges g h w'l'fill the threads formed by the cutting bits and thus prevent thecutting bits deviating in the east from a true circular path. In otherWords, were itnot that the trailing edges 9 h rested on the bottom i ofthe thread 7', an uneven pull on one of the handles of the diestockwould cause the cutting bits to dig in, but supported as they are by thetrailing bits, this is impossible.

In the common form of dies of this character now in use, all of the bitsare cutting bits.- In other words, the edges 7r m of the trailing bits 1and 2 would be cutting edges as well as the edges cf, with the reliefcurves of the trailing bits projecting in the same direction as therelief curves of the cuttin bits. This arrangement not only requiredgreater power to operate the die-stock, but

the increased inward pressure of the dies would distort the pipe so,that there would be about as much resistance ofiered in backing off aswhen cutting. In my improved construction, only two of the bits do thecuttin thereby greatly reducing the resistance bot in cutting andbacking off, the trailing bits merely supporting and steadyin thecutting bits without adding to the friction or resistance. To stillfurther add to the free cuttingqualities of the bits 1 and 2 they areprovided with the concave faces n and 0. This feature will givesufficient clearance to enable the chips to roll off with a minimumamount of resistance.

The mouth 1" s t to (Figs. 2 and 3) of all the bits are the same taperand of the same distance from the center of a pipe when said dies are incutting position, and the teeth on the taper face or mouth of both thecutting and trailing bits cut. In other words, the relief of the tapermouth of both the cutting and trailing bits is projected in the samedirection, as shown more clearly at Fig. 3. The partially formed teeth11. 1), etc. (Fig. 2),

serve to remove the surplus stock on the pipe and form a lead for thefull teeth of the cutting bits 1 a and 2*. While the partially formedteeth of the mouth of the bits 1 and- 2 are cutters, the full teeth onsaid bits are trailers, with their'clearance curves 6 c projected inopposite directions to the clearance curves of their mouths, while theclearance curves a d of the full teeth of the cutting bits and theclearance curves of the partial teeth of the mouth of these bitscoincide.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is Thread cutting dies comprising the sections1 and 2, each section having a screw threaded cutting bit and a screwthreaded trailing bit, the bits of each section havin oppositelyprojecting clearance curves, saic curves projectin away from the centerof the Working circ e When the sections are in operative position sothat one edge of the teeth of the trailing bits will be the samedistance from the center of the Working circle as the cutting edges ofthe teeth of the cutting bits, each bit having a taper mouth With 10 theclearance curves projecting in the same JAMES F. CRUDGIN'ION WitnessesJOHN B. CLAPP, GEORGE W. FINN.

